Development of Atomic Theory
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Questions and Answers

What fundamental idea did John Dalton contribute to atomic theory?

  • Atoms have a spherical shape.
  • Atoms are made up of positive and negative charges.
  • Atoms can be divided into smaller particles.
  • All objects are composed of indivisible particles called atoms. (correct)
  • Which statement about Democritus’s concept of atoms is true?

  • Atoms are the smallest units that matter can be divided into.
  • All materials are fluid and can change shape.
  • Atoms are made up of electrons and protons.
  • Atoms can exist in isolation. (correct)
  • In J.J. Thomson's model, which part of the atom contains negative charge?

  • The nucleus
  • The spherical jelly
  • The electrons (correct)
  • The atomic mass unit
  • What was J.J. Thomson's model of the atom called?

    <p>Plum Pudding Model</p> Signup and view all the answers

    What does Rutherford's atomic model propose about the structure of the atom?

    <p>Atoms have a positively charged nucleus with electrons orbiting in fixed paths.</p> Signup and view all the answers

    What misconception might be drawn from John Dalton's atomic theory?

    <p>All atoms are indivisible.</p> Signup and view all the answers

    Which statement accurately describes Niels Bohr's contribution to atomic theory?

    <p>Electrons travel in distinct circular orbits around the nucleus.</p> Signup and view all the answers

    What is the primary concept of Schrödinger's quantum-wave model?

    <p>Electrons behave as waves and can be described mathematically.</p> Signup and view all the answers

    What did James Chadwick contribute to atomic theory?

    <p>He proved the existence of neutrons.</p> Signup and view all the answers

    Which law states that the total mass of substances remains constant during a chemical reaction?

    <p>Law of Conservation of Mass</p> Signup and view all the answers

    What is a key postulate of Dalton's Atomic Theory regarding compounds?

    <p>The relative numbers and kinds of atoms in a compound are constant.</p> Signup and view all the answers

    Which atomic model is best associated with the idea of electrons existing in fixed circular orbits?

    <p>Planetary model</p> Signup and view all the answers

    What does the Law of Definite Proportions state?

    <p>The ratio of elements in a compound remains constant.</p> Signup and view all the answers

    What does the wave function Ψ represent in quantum theory?

    <p>The probability density of an electron</p> Signup and view all the answers

    Which quantum number describes the distance between the nucleus and the electron shell?

    <p>Principal quantum number</p> Signup and view all the answers

    How many neutrons does an atom of carbon-14 contain?

    <p>7</p> Signup and view all the answers

    What is the maximum number of electrons that can be accommodated in the fourth shell?

    <p>32</p> Signup and view all the answers

    What is the total number of nucleons in an atom of sodium-23?

    <p>23</p> Signup and view all the answers

    Which of the following correctly represents the change in the electron count when sodium becomes a cation?

    <p>Loses 1 electron</p> Signup and view all the answers

    Which of the following statements about the principal quantum number (n) is true?

    <p>It determines the energy of an electron.</p> Signup and view all the answers

    For the element iron-19, how many protons are present?

    <p>9</p> Signup and view all the answers

    How many quantum numbers are required to completely describe the state of an electron?

    <p>4</p> Signup and view all the answers

    What is the number of electrons in the anion form of iron when it gains one electron?

    <p>10</p> Signup and view all the answers

    What characterizes an atomic orbital?

    <p>It's defined by a specific set of quantum numbers.</p> Signup and view all the answers

    Which of the following describes the behavior of electrons as the principal quantum number increases?

    <p>Electrons have higher potential energy.</p> Signup and view all the answers

    If an atom of carbon has 6 protons, how many electrons does it have when it is neutral?

    <p>6</p> Signup and view all the answers

    Understanding the electron density or probability density, Ψ^2, is crucial for which aspect of wave functions?

    <p>Predicting the distribution of electrons in space</p> Signup and view all the answers

    What is the atomic mass of sodium given its isotopic composition?

    <p>23</p> Signup and view all the answers

    In the notation for an ion, what does a negative charge represent?

    <p>Gain of electrons</p> Signup and view all the answers

    How many neutrons would an atom of gold with an atomic mass of 197 have?

    <p>119</p> Signup and view all the answers

    When discussing isotopes, which description is accurate?

    <p>Isotopes have the same number of protons but different masses.</p> Signup and view all the answers

    Which atomic model emphasizes that most of an atom's volume is an empty space?

    <p>Nuclear model</p> Signup and view all the answers

    What was the primary conclusion from Rutherford's α Scattering Experiment?

    <p>Most of the mass of an atom is concentrated in the nucleus.</p> Signup and view all the answers

    What distinguishes the nucleus of an atom as described in the nuclear model?

    <p>It holds both protons and neutrons.</p> Signup and view all the answers

    Why did most alpha particles pass through the gold foil unscattered in Rutherford's experiment?

    <p>The nucleus is mostly empty space.</p> Signup and view all the answers

    What neutral particle was discovered by James Chadwick?

    <p>Neutron</p> Signup and view all the answers

    What model of the atom did Thomson propose based on his discoveries?

    <p>Plum pudding model</p> Signup and view all the answers

    What does the Law of Multiple Proportions state about the masses of B that combine with a given mass of A?

    <p>They are in the same ratio of small whole numbers.</p> Signup and view all the answers

    What was J.J. Thomson's significant contribution to atomic theory?

    <p>Identification of electrons.</p> Signup and view all the answers

    Study Notes

    Development of Atomic Theory

    • Democritus (600 BC) proposed the existence of atomos – fundamental indivisible particles.
    • John Dalton (1803) proposed the solid sphere model, stating that all matter is composed of atoms – indivisible solid spheres. His postulates included the Law of Constant Composition, the Law of Conservation of Mass, and the Law of Multiple Proportions.
    • J.J. Thomson (1897) discovered the electron through his cathode ray tube experiments, leading to the plum pudding model, where electrons were embedded in a positively charged sphere.
    • Ernest Rutherford (1911) conducted the alpha scattering experiment, revealing the nuclear model: a small, dense, positively charged nucleus surrounded by mostly empty space containing orbiting electrons.
    • Niels Bohr (1913) proposed the planetary model, where electrons orbit the nucleus in specific energy levels or shells.
    • Erwin Schrödinger (1926) developed the quantum-wave model, describing electrons as matter waves and introducing wave functions (Ψ) to describe electron behavior.
    • James Chadwick (1932) discovered the neutron, a neutral particle residing in the nucleus.

    Atomic Structure and Subatomic Particles

    • Atoms contain protons (+ charge), neutrons (neutral charge), and electrons (- charge).
    • The nucleus contains protons and neutrons; most of the atom’s mass is concentrated here.
    • The atomic number (Z) equals the number of protons and defines the element.
    • The mass number (A) equals the number of protons plus neutrons (nucleons).
    • Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
    • Ions are formed when atoms gain or lose electrons, resulting in a net charge. Cations have a positive charge (electron loss), anions have a negative charge (electron gain).

    Quantum Numbers and Atomic Orbitals

    • Quantum numbers describe the state of an electron in an atom. Four quantum numbers are used.
    • The principal quantum number (n) determines the electron shell and energy level (n = 1, 2, 3…); higher n means greater energy and distance from the nucleus. The maximum number of electrons in a shell is 2n².
    • Wave functions (Ψ) describe the behavior and location probability of electrons, ψ² is the probability density (electron density).
    • Atomic orbitals are regions of space where there's a high probability of finding an electron; each orbital is represented by a specific set of quantum numbers.

    Mass of Atoms

    • Atomic mass is the weighted average mass of an element’s isotopes, taking their relative abundances into account.

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    Description

    Explore the evolution of atomic theory through history, starting from Democritus' proposal of indivisible particles to the contributions of Dalton, Thomson, Rutherford, Bohr, and Schrödinger. This quiz will test your knowledge on key models and concepts that shaped our understanding of atomic structure.

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